Hydraulic boat lift

ABSTRACT

The present invention relates to a hydraulically operated boat lift capable of raising a boat vertically from the water in a linear fashion using a single hydraulic ram having its piston integral to the stationary frame and its cylinder integral to the non-stationary lifting portion of the apparatus. The ram raises a supporting crossbars under the front and rear of the boat. This single ram eliminates the critical problem of power distribution, binding, and levelness during raising and lowering. This simplified linear lift enables greater lift distances and also reduces and limits the extreme stresses that non-linear radius swing arm mechanisms experience thereby enabling construction with lightweight metals or plastics.

FIELD OF THE INVENTION

The present invention relates to boat docking apparatus . . . and, more particularly, to a boat lift for raising boats from the water using hydraulic power.

BACKGROUND OF THE INVENTION

This invention relates to an hydraulic boat lift for lifting a small boat out of the water when not in use and safely supporting such boat above the surface of the water. In addition, the apparatus also lowers the boat gently into the water for use. More particularly, the invention relates to such a boat lift which is operated by water pressure supplied by a domestic water supply or a pump supplying water from the body of water in which the boat is moored.

It is frequently necessary, or desirable, that a boat owner elevate his craft above the surface of the water in which it is being used to protect the same during inclement weather, storms and the like. Unfortunately, due to the complicated structure of conventional boat lifts, their expensiveness to fabricate, and the human energy which must be expended to operate them, most boat owners have been unable to obtain a satisfactory boat lift which is not only easy to assemble but requires little exertion to operate.

It thus has been an object of this invention to provide a mooring device for small boats, which device may rest upon the bottom of a lake or other body of water, such as alongside of a dock or the like, and which incorporates a hydraulically operated rectangular frame upon which a boat may be floated and thereafter lifted out of the water and held in a safe mooring position, wherein the boat is substantially unaffected by wave action.

It is often desirable for a boat owner to be able to store a boat elevated above the water to protect against attack by marine organisms and accidental sinking. It is also desirable to have a lift that can be operated without electric power for safety and because electric power may not be readily available.

U.S. Pat. No. 5,919,000 issued Jul. 6, 1999 to Unkle entitled Hydraulic Boat Lift

U.S. Pat. No. 4,773,346 issued Sep. 27, 1988 to Blanding.

entitled Hydraulic Boat Lift

U.S. Pat. No. 6,695,533 issued Feb. 24, 2004 to Bulman entitled Boat Hoist Hydraulic Lift Device

U.S. Pat. No. 5,522,671 issued Jun. 4, 1996 to Keesling entitled Hydraulic Boat Lift

The related inventions by Unkle relies on a very common approach in the industry that incorporates swing arms to guide and evenly distribute the power during lifting and lowering the boat. This approach although rugged, severely limits the usable lift range distance and, since the boat is lifted in a non linear fashion, the frame of the apparatus experiences massive stresses at the lower portion of the lift range. This extreme force requires the frame to be built of strong metals that are heavy and expensive to ship and waterproof.

The related invention by Blanding and also the related invention by Keesling both rely on a multiple hydraulic rams at different lift points. This approach requires additional expensive and complicated apparatus to ensure the device raises and lowers in a trouble free manner. If this additional apparatus is omitted, the device will definitely fail because the hydraulic power will be hoarded by whichever ram unsticks and moves first causing the device to instantly bind and jam. Similarly, during lowering, the device will descend unevenly and instantly bind and jam.

The related invention by Bulmann relies on a horizontally mounted hydraulic ram mounted within and moveable up and down within a horizontal member. This approach requires excessively complicated and bulky hardware and excessive crossmembers to transfer the heavy lifting forces from the lifting ram to the lifting frame.

It is therefore an object of the invention to describe a simplified apparatus to raise a boat using hydraulic power in a vertical and linear fashion to extend the lift range and limit stresses on said apparatus.

It is another object of the invention to raise a boat using hydraulic power provided by a single simplified hydraulic ram to avoid leveling, binding, and power distribution problems.

SUMMARY OF THE INVENTION

The present invention relates to a hydraulically operated four point boat lift capable of raising a boat vertically from the water in a linear fashion using a single hydraulic ram. The ram raises a supporting cradle under the boat at four corner points. This single ram eliminates the critical problem of power distribution, binding, and levelness during raising and lowering. The linear lift enables greater lift distances and also reduces and limits the extreme stresses that non-linear radius swing arm mechanisms experience thereby enabling construction with lightweight metals or plastics.

These and other objects, features and advantages of the invention will become more apparent when the detailed description is studied in conjunction with the drawings, in which like reference characters designate like elements in the various drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A complete understanding of the present invention may be obtained by reference to the accompanying drawings, when considered in conjunction with the subsequent, detailed description, in which:

FIG. 1 is a perspective view of a preferred embodiment of the invention.

For purposes of clarity and brevity, like elements and components will bear the same designations and numbering throughout the FIGURES.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a perspective view of the invention. The overall strength of the device is provided by the PVC four post pipe frame 1. Since this pipe frame is made of waterproof PVC plastic, it can rest stationary in the water without concerns of rusting. Because it is also lightweight, it can easily be positioned at the waters edge as tides or lake levels change. The Front of boat supporting crossbar 2 holds the weight of the bow of the boat and can be wrapped in carpet to cushion the boats hull. Similarly, the Rear of boat supporting crossbar 3 holds the weight of the stern of the boat and can be wrapped in carpet to cushion the boats hull. Optionally, two conventional trailer bunk boards could span both of these crossbars perpendicularly to further guide the boat into place and also further strengthens the overall apparatus. A larger PVC pipe is lowered upon and shrouds one of the frames post and forms the Hydraulic ram cylinder 4. This unique post serves two purposes. It is both inherently part of the frame and it is utilized as the Hydraulic ram piston 5. Unlike the other three frame posts, this post must have it's top capped to hold back the hydraulic pressure. Also attached to the top of this post is the Hydraulic ram rubber seal 6 that holds the hydraulic pressure as the cylinder rides up, down or simply rests stationary under static pressure. At the top of the hydraulic ram are two water ports for attaching two hydraulic hoses. The Hydraulic ram water entry hose 7 brings water into the ram from a valve operated by the user when lifting of the boat is desired. The Hydraulic ram water exit hose 8 is connected to a valve operated by the user to release pressure when lowering the boat is desired or simple to purge air from the system. During operation the cylinder exerts approximately ¼ of its force to raise one end of the Front of boat supporting crossbar 2 that is rigidly mounted and integral to the rams outer cylinder. The remaining ¾ of the ram lifting force is exerted on the Lift point for cables one, two, and three. 9. positioned over the Entry point to pulleys for cables one, two, and three 10. In order to direct and distribute the pulling force on these three cables, simple pulleys are mounted within the frame to route each cable through the frame and exit at their respective lift areas shown as Load lift area for cable one 11, Load lift area for cable two 12, Load lift area for cable three 13.

Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the example chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention.

Having thus described the invention, what is desired to be protected by Letters Patent is presented in the subsequently appended claims. 

1. A hydraulic boat lift for linearly raising and storing a boat above water using a single hydraulic ram having its piston integral to the stationary frame and its cylinder integral to the non-stationary lifting portion of the apparatus, or, having its cylinder integral to the stationary frame and its piston integral to the non-stationary lifting portion of the apparatus. comprising: a lightweight PVC plastic or metal pvc four post pipe frame, for supporting the overall apparatus and the raised boat; a lightweight PVC plastic or metal front of boat supporting crossbar, for supporting the front of the boat, concentrically retained to said PVC four post pipe frame; a lightweight PVC plastic or metal rear of boat supporting crossbar, for supporting the rear of the boat, concentrically retained to said PVC four post pipe frame; a hydraulic ram cylinder, for retaining the hydraulic pressure during operation; a hydraulic ram piston, for transferring the hydraulic pressure from the ram to the load, rigidly fused to said PVC four post pipe frame; a soft, flexible, and compressive hydraulic ram rubber seal, for retaining the hydraulic pressure and yet allowing he piston to move up and down within the cylinder, concentrically positioned to said Hydraulic ram piston, and concentrically positioned to said Hydraulic ram cylinder; a flexible hydraulic ram water entry hose, for supplying pressurized water to the hydraulic ram, hydraulically coupled to said Hydraulic ram cylinder; a flexible hydraulic ram water exit hose, for removing water or air from the hydraulic ram, hydraulically coupled to said Hydraulic ram cylinder; a lift point for cables one, two, and three, for providing a strong tie point to attach the three load cables to the hydraulic ram, rigidly connected to said Hydraulic ram cylinder; a load lift area for cable one, for attaching cable one to the front crossbar, internally connected to said Lift point for cables one, two, and three, and vertically attached to said Front of boat supporting crossbar; a load lift area for cable two, for attaching cable two to the rear crossbar, internally connected to said Lift point for cables one, two, and three, and vertically attached to said Rear of boat supporting crossbar; and a load lift area for cable three, for attaching cable three to the rear crossbar, internally connected to said Lift point for cables one, two, and three, and vertically attached to said Rear of boat supporting crossbar.
 2. A hydraulic boat lift for linearly raising and storing a boat above water using a single hydraulic ram having its piston integral to the stationary frame and its cylinder integral to the non-stationary lifting portion of the apparatus, or, having its cylinder integral to the stationary frame and its piston integral to the non-stationary lifting portion of the apparatus. comprising: a lightweight PVC plastic or metal pvc four post pipe frame, for supporting the overall apparatus and the raised boat; a lightweight PVC plastic or metal front of boat supporting crossbar, for supporting the front of the boat, concentrically retained to said PVC four post pipe frame; a lightweight PVC plastic or metal rear of boat supporting crossbar, for supporting the rear of the boat, concentrically retained to said PVC four post pipe frame; a hydraulic ram cylinder, for retaining the hydraulic pressure during operation; a hydraulic ram piston, for transferring the hydraulic pressure from the ram to the load, rigidly fused to said PVC four post pipe frame; a soft, flexible, and compressive hydraulic ram rubber seal, for retaining the hydraulic pressure and yet allowing the piston to move up and down within the cylinder, concentrically positioned to said Hydraulic ram piston, and concentrically positioned to said Hydraulic ram cylinder; a flexible hydraulic ram water entry hose, for supplying pressurized water to the hydraulic ram, hydraulically coupled to said Hydraulic ram cylinder; a flexible hydraulic ram water exit hose, for removing water or air from the hydraulic ram, hydraulically coupled to said Hydraulic ram cylinder; a lift point for cables one, two, and three, for providing a strong tie point to attach the three load cables to the hydraulic ram, rigidly connected to said Hydraulic ram cylinder; an entry point to pulleys for cables one, two, and three, for routing the three load cables to the simple pulleys within the tubular frame; a load lift area for cable one, for attaching cable one to the front crossbar, internally connected to said Lift point for cables one, two, and three, and vertically attached to said Front of boat supporting crossbar; a load lift area for cable two, for attaching cable two to the rear crossbar, internally connected to said Lift point for cables one, two, and three, and vertically attached to said Rear of boat supporting crossbar; and a load lift area for cable three, for attaching cable three to the rear crossbar, internally connected to said Lift point for cables one, two, and three, and vertically attached to said Rear of boat supporting crossbar. 